锅炉水压试验的目的有( )。
A.决定锅炉的工作压力
B.计算锅炉热效率
C.避免出现事故
D.检查受压部件的严密性
E.检查在一定压力下是否有残余变形
参考答案:D,E
The population of the province to more than twice what it was in 1949. The figure is now approaching 74 million.
A.are growing
B.have grown
C.grew
D.has grown
哪些鱼类以肛长表示鱼体长度()
A、带鱼
B、黄鳝
C、鳗
D、鲶